Effects of BP 2-94, a selective H-3-receptor agonist, on blood flow and vascular permeability of the rat mandibular incisor pulp

Pulpal blood-flow changes were monitored by laser Doppler flowmetry after e lectrical stimulation of the mandibular incisor. Stimuli of 10 s (50 muA, 2 ms, 20 Hz) were applied to the incisors of untreated animals and longer st imulations (5 min) were applied in animals treated with the a-blocker pheno xybenzamine. Changes in vascular permeability in the dental pulp were measu red by Evans blue extravasation following resection of the superior cervica l ganglion. In these groups, a selective agonist of H-3 receptors, BP2-94 ( 1.5 and 15 mg/kg), and an H-3-antagonist ciproxifan (1 mg/kg) were administ ered. The effects of these drugs were compared with those obtained from ani mals treated only with the vehicle (methylcellulose 1%). Basal pulpal blood -flow was not affected significantly by BP2-94 or ciproxifan. The vasoconst riction induced in the group of intact rats by electrical stimulation of 10 s was decreased in amplitude and duration at the higher dose of BP2-94 by 58 and 40%, respectively (P < 0.05, n = 5). In the sympathectomized animals , plasma extravasation was significantly increased at 15 mg/kg BP2-94 (+ 10 0%, P < 0.01, n = 5). These results suggest that H-3 receptors may particip ate in the regulation of changes in vessel contraction and permeability pro voked by electrical stimulation of the dental pulp. However, the non-select ive effects of the H-3 agonists reacting on adrenergic sites and H-1 recept ors could explain a part of the results. (C) 2000 Elsevier Science Ltd. All rights reserved.